1. Technical Field
The present invention relates to a method of repairing a composite material, and also to a composite material having been repaired.
2. Related Art
As a skin forming the outer face of an aircraft wing, a composite material that is composed of laminated plural sheets of CFRP (Carbon Fiber Reinforced Plastics) or the like has been used.
The skin is arranged on the front and back sides of the wing with a distance therebetween, and is constructed in a box shape together with spars that form the front and rear edges of the wing, respectively. The boxed space is provided with ribs for supporting the skin on the front and back sides, and is utilized for housing various devices and fuel.
Incidentally, when the skin is damaged due to undergoing an impact, repair becomes necessary. The repair is made in a manner in which the damaged part suffered laminate exfoliation due to the impact is removed, and a concave portion formed by removing the damaged part is filled with a composite material. It is desirable to carry out the repair without disassembling the box-shaped structural body.
If the damage does not reach the back side of the skin, it is possible to repair the structural body by approaching from the front side (one side) of the skin without disassembling the structural body.
For example, onto the concave portion formed by that the damaged part is removed from the front side, a semi-hardened repair material, which is a similar composite material as the skin and is overlaid on a film-like adhesive, is placed. The repair material can be bonded to the composite material by heating and curing the repair material after the repair material and the composite material get close contact with each other through the adhesive by being evacuated from the front side. Since it is desirable that the concave portion of the composite material has a shape equalized in every direction in order to avoid stress concentration, the concave portion is formed in a mortar shape, the plan view of which is circular, through scarf machining.
On the other hand, if the damage has reached the back side of the skin, the concave portion formed by removal of the damaged part passes through the composite material in the thickness direction, and a through hole having openings on both front and back sides is formed. It therefore becomes necessary to block the opening on the back side in advance of evacuation, which needs a worker to enter to the back side. However, if it is not possible for the worker to enter the boxed space, the structural body has to be disassembled.
A method of blocking the back side opening of a through hole by forming the through hole and a patch for blocking thereof in an oval shape is described in Aircraft Icing Handbook, Report #DOT/FAA/AR-08/54 Composite Maintenance and Repair Issues. In contrast to the case in which the through hole and the patch are formed in circular shapes having substantially identical diameters, it becomes possible to cause the patch to be delivered to the back side by vertically orienting the patch such that the short axis of the patch meets the long axis of the through hole. Then, the through hole is sealed by the patch that is turned on the back side.